Im building the extra also. For the spar I just used the dremel router attachment. Works great. Work very slow and on a straight edge. I used a smaller dia. spar though because in order to fully seat the spar It would of left a millimeter of foam left after cutting it. And since my basement is filled with all shapes of sizes of carbon rod. Why not.
EVerything is set up .. I used robart hinges and half of them glue got dried on the hinge point. and once there glued in. nothing to do exect pull. And off goes half the wing. oops... on the elevator i had and rudder i had to revert to tape. Wing i got some fixxing to do.